


Serious

by FionasEmbrace



Category: Big Hero 6 (2014)
Genre: Age Swap, M/M, Sibling Incest, Trans Male Character, Trans!Hiro, Younger!Tadashi, older!Hiro
Language: English
Status: Completed
Published: 2015-10-31
Updated: 2015-10-31
Packaged: 2018-04-29 01:56:10
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 5,772
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5112071
Author URL: https://archiveofourown.org/users/FionasEmbrace/pseuds/FionasEmbrace
Summary: <blockquote class="userstuff">
              <p>"I don't mean to swear. I really didn't, it just came out. Sorry, Tadashi." The college kid affectionately mussed up Tadashi's hair. "I know you really wanted to make the practice on time."</p><p>Tadashi peeped out the window, sadly. "I guess I can't go, now." He slouched against the car seat. "Hiro."</p><p>"Yeah?"</p><p>"What other kinds of things would you do for me, if I asked you to?"</p>
            </blockquote>





	Serious

**Author's Note:**

  * For [jokulfrosti1](https://archiveofourown.org/gifts?recipient=jokulfrosti1).



> This is by special request for jokulfrosti1, off of Tumblr. The request was: "Submissive!Older Hiro, Dominant!Young Tadashi, Trans!Hiro, which Tadashi doesn't know about beforehand." enjoy!
> 
> This was my first time writing about a transgender character- I just sort of wrote what I thought would be hot, without agonizing about it too much. I am very receptive to feedback, so if I got something really wrong please let me know and I'll adjust it. I really enjoy reading other people's trans canons and stories. So today's a good day that I would finally write one too.
> 
> I don't really know what Tadashi's age is supposed to be. While this is flagged as age swap, Tadashi's lines inadvertently ended up sounding a bit 'cute'.

That dark evening, the city streets were still alive and busy. Until he grew up and became more independent, it would always be like this. Getting his older brother to ferry him around. Tadashi gazed absently out the car window as everything skated by. The boy asked his older brother, "Can you drive faster? We're gonna be late."

"I'm going as fast as I can." Suddenly, Hiro laid down the brake. Hard. "Shit."

"You swearer!" Tadashi gasped, more interested in chiding his older brother's language than anything else. The chain of cars ahead of them had come to an abrupt stop, leaving Hiro little time to react, and he was going at a healthy speed to start with.

"Yeah, yeah. Are you okay?"

"Mm-hmm."

"Lemme see what's going on." Hiro murmured, stepping out of the car, and he peered on ahead. What could it be? Some accident? A closure? He put his hands in his pockets, feeling the chilly wind.

Up ahead, beyond the statue garden and the commercial complex where they were, he saw it. Of course. Of f'ing course. He sighed in exasperation, and got back into the car.

"Parade."

"What?"

"Did you notice what day it was, today?" He looked at Tadashi, as if it should've been his job to remind him.

"Why, is it... oh!" He realized it, too. It was none other than the national memorial holiday, commemorating the founding of the city, complete with huge festivities and fireworks. The day after tomorrow, everybody got the day off. 

"Crap. Crap. I forgot... And, the other closures downtown." It was that entire block, and the connecting streets near it all the way to the oceanfront. "Now, we're stuck. Unless-" Hiro glanced around. It was that same expression. Tadashi recognized it. He could literally see the gears turning, and felt nervous. 

That expression he made, whenever he was about to do something rash. Something _dangerous_. "Just one sec-" Before Tadashi could ask him what he was about to do, he gripped the wheel and put the car into gear. Veering abruptly to the left, he brought them out of the gridlock and into an alleyway obviously not intended for street traffic. Avoiding some trash recepticles and clotheslines, he emerged out into the cross-street on the other side. It was a true miracle, all thanks to Hiro's quick thinking and general fearlessness. 

Now safely back on the open street, they were now conveniently facing the opposite direction from where they were supposed to go- Tadashi's evening kickboxing practice.

"At least now, we're not stuck."

"You always swear, and you say mean things, and then Aunt Cass hears it and gets mad at you." He pouted, disapproving.

"I don't mean to swear. I really didn't, it just came out. Sorry, Tadashi." The college kid affectionately mussed up Tadashi's hair. "I know you really wanted to make the practice on time."

"I _did_." Tadashi peeped out the window, sadly. "I guess I can't go, now." He slouched against the car seat. "Hiro."

"Yeah?"

"What were you gonna do, while you wait for my practice?" This session was usually about two hours, pretty boring to just sit there.

And Hiro wasn't one to do that. "You want the honest truth?"

"Uh-huh."

"Definitely not a botfight in the basement underneath Lot 5." This was, as even Tadashi understood it, a particular shady commercial district. One a few minutes drive away from where they were, but far enough away from the downtown waterfront.

"You weren't!"

"Lately- they keep on using the exact same rigs, the exact same components, the exact same stupid tactics. It's like shooting fish in a barrel. It's all I can do to throw the right matches once in a while, to convince them there's no foul play."

"It doesn't matter whether you win or not." He frowned. "You gotta stop botfighting, Hiro. 'Cause you got in trouble for it before. It's against the rules."

"I will stop. After this one match."

"No-" Not that. Not _that_ look. Those adorable puppydog eyes. God damn, god damn they were hard to say no to. "Right now."

"Why?"

"Or I'll tell."

"You'll _tell_." He chuckled to himself and stopped the car at a red light, waiting for some pedestrians to pass.

"You think I won't tell Aunt Cass? Last time, she found out. You remember, having to go to the city jail like that. I'll tell her, and she'll be soooo mad."

"Like I give a shit!" Okay, so he really did think he would swear off the botfighting. But, the _money_. Even with the process if growing older, Hiro's rebellious phase never completely ended. 

And then there was how the coursework at SFIT only occupied a paltry amount of his time and brainpower. The most grueling robotics term papers, the toughest theoretical physics course was a total and complete non-issue for him. Therefore, he had turned to more _colorful_ pursuits. The money was just a nice extra. What could be more exciting- or more profitable- than the underground botfighting scene? And if only his cute, adolescent voice of reason sitting in the car beside him weren't on his case.

"Okay." Tadashi murmered. 

Now that the light was green, the older brother started forward once again, but glanced over and saw Tadashi taking out his cellphone. It was only a year ago that he'd got it. He was happy with the newfound sense of independence. "W-wait-"

"I'm really gonna do it."

"Stop-stop stop stop. Stop." The boy looked up innocently from the phone, about to dial up their aunt. 

"No. Make me."

"Oh, for-" Hiro pulled over into the nearest available spot. It was a secluded parking lot at the back of a vacant store, with a stack of old tires on the porch. Given it was night-time and the place was poorly lit- their only means of seeing where the pavement ended were their car's headlights. Hiro put the thing in park, and turned off the engine, expecting a confrontation. They'd had episodes like this where Tadashi threated to snitch on the botfighting to Aunt Cass, but they were always empty threats- this seemed _real_.

"How about I'll give you half my winnings. That's good, right? How about it?"

"Umm, I dunno."

"It's this much-" He told him the amount, and Tadashi's eyes lit up. That was a hell of a lot of money. Basically- it was twice his allowance over, for the whole year. Endless lunch money! All the comic books he'd ever want!

"That's an insane amount of money!"

"A lot of even the middle-tier people don't _need_ to work. It's that good." There was some element of how much Hiro loved playing this off like it was no big deal.

"I don't know, though."

"Seventy-five percent?"

"If she finds out that I knew, and didn't say anything, you know- I'll be in trouble too."

"Naw, she'd never blame you. Don't be silly."

"That's what you think. 'Cause you don't live with us anymore. I still get grounded for stuff."

"What if I gave you one hundred percent? Literally, all of it. All of the winnings for today. And you won't say anything after that."

"I just don't care that much about money."

The older brother sighed. "Of course. 'Course you don't." He'd forgotten, that Tadashi was still not at a point yet where money would totally change his life. It was the difference between comic books or no comic books, new video games or playing the ones he already had. How could it ever make a world of difference, which?

And more than that, for better or for worse, he lacked the real propensity for materialism Hiro had at his age. But a wave of something sinister came over the young boy's face. "I'll forget all about it, if..." his eyes narrowed. "you suck my dick."

"What?!"

"I know you do a good job."

Hiro took a moment to figuratively pick himself off the floor. Rationalize things, and process what was just said to him. "Why-"

"I can hear it. I can hear you sometimes from over the wall, you know, it's hard not to hear, it makes all those gross noises. I heard it when-"

"That is completely, like... you shouldn't be listening to that!"

"I mean, I didn't _see_ anything."

"It doesn't matter if you _saw_ anything. You shouldn't be listening to me, um-" he searched around for the right words, and then sheepishly found it- " _having a private time_ with someone. Just go look at some porno or something."

"I didn't even listen on purpose. Cass wasn't home, and it was too loud not to hear."

"Look, it's my bad. I'll try to keep stuff more quiet next time, okay?"

"So, you'll do it?"

"We are _blood related_. You know that, right?!"

"And I guess that makes it wrong."

"Like, _genetically_. Yes, that makes it wrong. I thought you cared about things like that. Right and wrong. Don't you? About getting into trouble."

"I just really, really want it, Hiro. I know you're my big brother and you're a lot older than me. I don't care if it's wrong or not."

"You're serious."

"I've been wanting it for a while. But I was too scared to tell you."

"I didn't even know you were beginning to get interested in... _that_?!"

"Um, I don't know exactly when it started. Now, if I touch it down there, white stuff comes out... And it gets hard sometimes. Actually, almost all the time. Usually, at all the wrong times."

"You don't have to talk like you don't know what it is. You know what it's called."

"It's, um... It's hard, right now." Tadashi looked down, and blushed. Hiro couldn't see it from where he was sitting, but he took his younger brother's word for it. 

He forcefully collapsed back against the seatback, staring forward through the wind-shield at the graffitti-ed brick wall they were facing, contemplating how life had possibly taken him down this path today. Down the path of doing something like _this_ , with his own brother. Even compared to botfighting, it was sure as hell a terrible idea. 

But, maybe it _wasn't._

What if it wasn't? What if this was really all it took to shut Tadashi up? In some respects, that would be a pretty good deal. And, deep down, this was something he would take to his grave and _holy hell it was so wrong_ and _never ever tell anyone_ but the thought of doing something with Tadashi had crossed his mind before. Maybe if only for a split second. Why? He didn't know. He loved Tadashi, in all of the 'correct', 'normal' ways, so that part was fine. Something about the person Tadashi was growing up into, and the relationship they'd come to have together... It was nothing he could fully explain. Nothing he could admit to himself. And so, what. Everyone thinks about things, it doesn't mean that you act on them. 

But here he was, and there was that _way_ Tadashi was looking at him. Different situations, but he'd seen it before. Those captivating, pleading eyes. Not too much unlike his own, but in his opinion, more beautiful. It was utterly irresistable and impossible to say no to. 

"You want this. You're a thousand percent sure. And you won't tell Aunt Cass about the botfighting?"

"Please, Hiro." That look involved the cutest puppydog eyes, and it certainly came in handy whenever he tried to pull off asking for things. "I promise, if you do it, I'll keep this- and the botfighting- a secret. Bro code, top clearance-level secret."

The man sighed, and looked the tiniest bit more closely down at Tadashi's lap to see if it was really true. There was what looked like a hardness in the boy's pants, although they were skinny jeans and it was hard to tell. In this unprecedented moment of assertiveness, Tadashi took Hiro's hand, and placed it on his lap, touching the stiff member through his jeans. He still had some growing to do. But Hiro could definitely feel it. His eyes shot open, as he processed what _it_ was. No. It was hard to even accept the thing he felt, underneath those cute skinny jeans. His younger brother's erect dick. 

"Can you feel it, Hiro?" 

"Yeah. I can."

"It got hard. For you."

"Man, where did you learn to talk so dirty?"

"Mmmh-" Long, deft fingers went up and down Tadashi's cute length through the jeans. He flailed around a little bit on the seat, unused to being given attention like this. Even through the layers, it felt exquisite, he just wanted more and didn't care how he'd get it. Hiro was good with his fingers, and didn't get bored. 

But, it wasn't enough. Tadashi was impatient. He wanted to pull Hiro down by the face and ream it down the man's throat and fuck the logistics or whether it was a good idea. He needed it _yesterday_. "Please, Hiro-" He undid his own fly, and pulled out his hard member. Hiro was a bit surprised at how forward he was. And what a strange moment this was- it was his first time- really, it should have been his neverth time- seeing Tadashi's erection. 

Yes, it was dark in the car, there was only the mostly-occluded streetlamps and some illuminated signs from the divey places further away. There was scattered shadows everywhere, but this was enough. He could see it, and feel it. Tadashi pulled Hiro's hand over it, and the older Hamada felt a shameful bead of pre-cum dripping from the head. He heard a small gasp as he stroked it, from the base to the tip, and Tadashi leaned into it, pushing his hips forward to just try and get more. Something. Anything. He wanted it from Hiro, more than he could even get in words, more than anyone in the whole world. 

"Please-" He ran his thumb over Hiro's lips, and tried to look seductive. Something he'd seen on the internet, no doubt. But it worked. Damn right- Hiro glanced down at the thumb prodding his mouth, the hard dick underneath his fingers, that _pleading_ , _beautiful_ look from his own flesh-and-blood brother. The tiny fingers dipped against his lips, and he kissed them and sucked them just a little. Tadashi loved how this looked, and his hips kept fucking the air and Hiro's lazy petting on him. As Hiro looked at it, it looked so perverse, so _forbidden_ , but there was just no resisting it. 

And it didn't help when the teen bravely took hold of the back of his older brother's head, and guided it down to his lap. As he complied, getting down there and gripping the boy's thighs, holding them slightly apart, Hiro couldn't help but smile. It shouldn't be, but it felt _cute_. This, and everything Tadashi did. Hiro tentatively licked the head of it, and Tadashi winced and screwed his eyes shut. It was so much sensation, so fucking much, more than he bargained for. 

Hiro ran a thumb over the head of it, pushing back against it just to see it bounce back into his face. Full mast, seriously. Tadashi writhed around in the chair, aching for whatever could happen next. Hiro took the opportunity to encase the whole length in his mouth. Right to the base, to Tadashi's barely-there pubes- maybe with a bit more effort he could nearly fit the balls in, too, but this was enough. The younger brother choked out a gasp. His little fingers trembled on Hiro's shoulders, caught between pulling him closer and pushing him away. Hiro glanced upward, their eyes meeting. And that was what did it.

"I- I'm sorry."

"Mmph?" He tasted it, and took the cock out of his mouth. Wow. "Did... did you-"

"Sorry. I, um- I couldn't help it! It was too good." Figured for that age, he would have zero lasting power whatsoever- one not-quite-deepthroat maneuver and that was it. Well, okay. Hiro wiped his mouth and swallowed down what there was, and figured that was much simpler than he initially thought. "But will you do it more?"

"Really. You can go again?"

"Uh-huh. Please."

Hiro didn't mind- he was impressed by Tadashi's investment in all this, honestly. "Alright." He gripped the softening penis with his thumb and forefinger, and very, very gently licked the sides. If he fisted the whole thing, it would leave practically nothing exposed. He was ever so gentle, taking care not to overstimulate Tadashi since he had just gotten off. Tadashi collapsed back in the chair, in total bliss, completely lost. 

"It- it's so good, Hiro! Please, do it more-" Hiro was about to come back with some smart-ass reply, but was taken off-guard. His eyes shot open, and his vision was taken over by his younger brother's dick thrusting into his face. Tadashi pawed at Hiro's shoulders, neck and face as he thrusted his hips hard into that tight, perfect mouth. It was fully hard now. With his newfound lasting power, he thrust in and out with all the energy in the world and _fuck_ it was so much better than anything he'd ever done by himself. Anything he could ever imagine.

Holy hell. It was just the right amount of tongue, the right amount of friction, he just wanted to cum in Hiro's mouth over and over. His teenage dick was just about to cum in Hiro's mouth for the second time- he had to stop himself. Had to slow down. But even more than that, what about Hiro? His brother, his own personal idol, and partner-in-crime here- how could he be so selfish? No. He gently pulled himself away from Hiro's face, lone trail of spit and pre-come form his cockhead to Hiro's lips.

"Now, lemme do you."

"What?!" Hiro wiped his mouth.

"It's your turn. I mean, it's only fair."

"You don't have to do that."

"Nuh-uh. You gotta let me." That tone of voice he used when he was playing around- it came off as sexy, somehow.

"Why? I thought you just wanted to get off."

"You don't think I'll be good at it? Like you get all the fun?"

"Well, no, I-"

"I promise, I watched a lot of stuff on the internet. I know how it works. How to do it. I know blowjobs."

"Really, you don't have to. It's okay."

"I wanna make you feel good too, Hiro. I promise I'll do my best."

He sighed. "It's okay."

Tadashi looked down at Hiro's cargo pants, below the young man's belt. "Are you hard now, too?"

"Right now? Um... I don't know."

"Lemme see." 

"H-hey!" Hiro felt the small fingers along his lap, and cup his groin, stroking his crotch through the pants. It all happened too quickly for Hiro to react too much to it.

"Aw." Tadashi looked a little bit disappointed. "You're not hard. It means you don't like me how I like you." Hiro looked at his brother, shocked, not knowing what to say. 

"Tadashi... Don't take it like that. Please."

"Don't worry." That sinister, perverted little smile came back. "I can help."

"Um- what?!"

"I know what to do. Here-" The boy climbed swiftly into Hiro's lap, shrugging off his undone pants in the process, narrowly avoiding hitting the car horn with his elbow. Hiro looked at Tadashi up and down, held the boy in his lap, and shamefully pushed his seat back. 

And then the younger one faced Hiro and started grinding his hips into his older brother's. Through only those briefs, Hiro could feel _every_ curve and part of his younger brother's developing body. How smooth and hairless his thighs were, and his tight little ass. What this was was a lap dance. Tadashi moved his crotch and ass insistantly against Hiro, and kissed him once again full on the mouth. Clearly yet another maneuver he'd learn from the internet, but damn if it wasn't effective. He slid his hands up Hiro's flat chest and rested them on his older brother's shoulders, and could vividly imagine them having sex. Tadashi was still hard as anything, the pre-come getting close to staining Hiro's shirt. 

That tight little body in his lap. His younger brother's perfect, cute face. Hiro screwed his eyes shut into the kiss and felt himself blush. This whole thing was out of control.

Finally, Tadashi halfway pulled away. "You like this. I can tell." He looked down, and helped himself to touching Hiro through the man's jeans. "But, you're still not-"

"Look, Tadashi. You can't just do whatever you want, and expect whatever you want. It doesn't work that way."

"B-but... why? Here, let me-" He reached down, unbuttoned and pulled down Hiro's jeans. Hiro was caught off-guard a little, and didn't bother to try and stop him. But then, the boy froze. Wide-eyed. Even with everything that happened between them until now, out of all the things in the known universe, Hiro did not see _this_ happening.

"I-it's... That's... You have-"

"I know."

"Down there-"

"I know. It all makes sense now, doesn't it."

"I just- I never thought that-"

"It's not what you were expecting, is it?"

"N-no. I mean, I've never seen you without your underpants on." He couldn't help but glance downward again, to instill upon himself what all this was.

"You have before, when we went swimming. But you were too young to remember."

"Hmm." Tadashi searched and searched his memory banks, but it came back blank. Because, it really was when he was only around two or three years old, barely off the ground. "Then it makes sense, that I never knew about it." 

"So, now you know. We can stop this now, then, since that's where this is going." Hiro sighed.

"No, I meant-" He looked a bit nervous. "Can I touch it?"

"What?" Hiro stopped in the middle of getting his pants back on. 

"Please."

He perred into those eyes, identical to his. It was quiet, still, in the darkness outside and inside the car. He had trouble getting a read on Tadashi. "Um, okay."

The younger boy reached down, and touched overtop Hiro's boxers, searching with his fingers through the fabric. No matter what body parts were involved, he had no fucking clue what he was doing, but hell if that could deter him. He stroked up and down the boxers, much as Hiro had done to him. Hiro couldn't lie, it did feel good. Despite the sheer lack of skill, Tadashi's fingers were gentle and a little bit shaky from his arousal and from nerves, which made the whole thing even better. 

And there was the slit in the boxers, mostly useless now. Not entirely. Tadashi snuck his fingers in the slit in the boxers. It was a good opportunity to poke around at what was beneath. Touching anyone, being intimate with another person, it was a real first for him and he wanted to do everything. But most of all, he wanted to do it with his beloved brother. To prove that he could do a good job, even when he lacked the experience of doing anything except masturbation by himself. 

His fingers poked, and prodded, and molested his brother, staring intently, _perversely_ at what he was doing. Oh god, how it _was_ so perverse- the way Tadashi seemed so utterly fascinated by it, his own little brother and precious little angel, always the furthest thing in the world from any of _this_. The shaky fingers, the perverted gaze, it was- he didn't know what to think.

"So, I know it's not what you were expecting, and all that. Now we can pack it up and go home."

Tadashi pulled away, and it seemed like he was about to agree. It seemed that way. "I want to fuck it."

"What?!"

"I'm still hard."

"Okay, and that's great for you-"

"I think it would make me feel good. And you too. So I want to do it. If I try, can I make it go in?"

"I- I don't know?! How can you possibly suggest something like that?!"

"We already did one dirty thing."

"You know, you act all nice and sweet to me, and to Aunt Cass. I don't know how you became so perverted!"

"Like- when my thing gets hard, touching it is okay. And a blowjob is good. But what I really, really want... especially right now, is to stick it in someone. It looks like I should fuck this. It should be easy."

"I am your _brother_ , Tadashi. What are you calling a _this_?"

"That means I can't make you pregnant, right?"

"No, that's not what that means."

He climbed up on top of Hiro, assuming his position once more on his brother's lap, and grinded his dick against it, insistently. Fuck, it felt good. Even on the awkwardness of the carseat, even through the underwear, every so often it would dip inside by the tiniest amount. All of it was made better by the fact that it was Tadashi. The fact that it felt _so wrong_. 

He shouldn't let Tadashi do this to him. This was his own brother, flesh and blood born of the same womb as him. The same one he had a hand in raising, himself, in absence of their parents. And as of exactly now, they knew literally everything about each other. It should be revolting. It should be out of the question. But it was _Tadashi_. Those eyes, impossible to resist. The fidgety little hands, exploring up his body. There was that hard, insistent dick pushing, trying to make its way into his boxers. And succeeding. Right and wrong be damned, Hiro could no longer resist the urge to do it. 

"Tadashi- y-you can-"

"I can do it?! Really?" His cute face lit up like Christmas morning.

"Yeah, but you can't act like we can do this all the time-"

"I know." He put his hands on Hiro's shoulders, and nodded. "But, it'll be good. Just watch."

He raised his eyebrows in a bit of skepticism, something he couldn't hide- then let the seat down. If this was really happening, he might as well fully admit it to himself. Tadashi playfully got on top of him, kissed him messily, and felt up Hiro's body. He got comfortable positioning himself right between the elder Hamada's legs. The younger brother was _so_ into it by now, he thrust his cock against Hiro, salivated at the kiss, and trembled from what he was doing. The kiss was hard and desperate. He looked like he was about to cum right then and there. 

The insistent shoving, grinding- of his brother's dick up into his boxers, until now, it'd been _dry_. Mostly dry. Tadashi reached down and felt the slit in the boxers, and pulled the fabric apart with his fingers, and fed his dick in. He didn't waste any time, definitely. The blunt lack of skill was painfully obvious with how he tried to simply shove his cock forward and achieve direct penetration, and of course, it didn't work. 

It took two, three, several more tries until he found the right place. Hiro felt it, but was skeptical it could really work without his help. Maybe it was a bit cruel of him but he liked watching Tadashi try. It grazed him. Every time it felt like it was about to go in, Tadashi would push it the wrong way or lose the positioning. It was hard to do it with no hands like this.

The moment when he was on the brink of giving up and intervening with his hands, he felt it. Hiro's eyes shot open as he felt Tadashi's length. The whole thing. Inside. It got roughly shoved deep inside of him, it was impossible for Tadashi to stop halfway, no matter how tight the resistance was. Holy shit.

"F-fuck, it's bigger than it looks-"

Tadashi wasted no time starting to thrust in and out. He smiled. "You're gonna be in trouble for swearing." He repositioned himself on top of Hiro and started literally pounding it. He knew now. He should have asked for _this_. It was better than by himself, better than a blowjob, he knew that much for certain. He loved how Hiro closed in around him, how it _felt_. He felt Hiro embrace him, holding him close, and he took it as encouragement to start doing it even harder. Even at Hiro's full adult height, he was shaken and rocked back and forth by the sheer impact of this. Tadashi pounding away mercilessly into him. He had impressive stamina, he'd give him that.

The boy raised himself into more of a push-up position on top of Hiro. They still had most of their clothes on- Hiro, especially- which made it really hot somehow. He liked how it looked- the visual aspect was a large part of it.

"I- I get to fuck my big brother..."

"Don't let it go to your head."

"I wanna do it over, and over..."

To think they had gone from something so routine as dropping Tadashi off at practice, to this. To intercourse. Tadashi had to threshold himself if only to not get too excited. But it was difficult to resist reaming Hiro's body, feeling every trembling reaction underneath him, totally and utterly dominating his big brother. Hiro let out a choked-out gasp, and kept one hand on Tadashi, the other gripping the car seat. 

The teenager pinned him down with his hands and body while he kept fucking him. He wasn't going anywhere. It went in a bit deeper now, but it was a tight one all the same. Tadashi actually started sweating a little, and something only just now occurred to him.

"Let me jack you off while I do it." Hiro looked down, at Tadashi's fingers, and nodded. The boy stroked his little fingers overtop Hiro's boxers, alongside all the _action_. He pinched at certain parts and could feel right where it was best. And then he worked it with his fingers, over and over, all while fucking at full force. Hiro's smug demeanor had worn away now, and he was simply lost, at the mercy of Tadashi's young cock. "I'm good at it, right?"

"Y-yeah, it's good."

He took it as encouragement, and changed up the angle a little. Even with the height difference, it was possible for Hiro to hook his legs around Tadashi and get it in that way. Easier access. Tadashi kept one grip on Hiro's thigh, holding it open, while he kept stroking his big brother. Where initially, he had to fight it a bit for entry, he no longer had to do that. He could shove it right in and out to his heart's content and treat it like it was his property. 

Certain things were true. Hiro would always be older than him, a kind of authority figure, taller for sure, and even smarter and better accomplished. It didn't get talked about much- it was kind of understood. This unspoken thing. But here and now, it didn't matter. He _had_ Hiro. He could make Hiro feel good, and that came with a sort of power for him, something impossible to resist. Who was so smart, now? No, he was not so innocent as Hiro liked to believe. 

"T-tadashi, if you- if you don't slow down, I'm gonna-"

Slow down? No, there was no way he'd do that. He wanted to see Hiro cum beneath him, _while being penetrated_ by him, then and there. Just how Hiro wanted it. He'd heard, but never seen Hiro get off before. He needed to watch it happen. This side of his big brother that he'd never known before. 

And then it happened. Hiro gazed off into space, then into _his_ eyes, and started to tremble. 

"J-jesus christ-" 

He felt it tighten around him, too. Hiro held their bodies flush close and he shoved it in as hard as he could. He kept fucking him all the while. It seemed to go on and on, a new spasm clenching around him every few seconds- until finally, Hiro released his grip on him and he was stll free to slide it in.

"Did you-"

"I came." Hiro tried to catch his breath, but he looked a mess.

"Was it good?"

"Uh-huh." He watched Tadashi start to pull it out. "But- you should finish, if that's what you want." Tadashi shot him a perverted look, and nodded, unable to articulate much of anything. And then he shoved it back in. Over, and over. He went so hard, and jackhammered it right into the car seat. He couldn't last, like this. 

"Hiro, I... I'm gonna-" He shot it, deep inside, even though it felt wrong and it was so messy. He couldn't resist. Hiro felt the seed filling him, even as his younger brother kept thrusting and depositing it deeper inside. It was a huge mess. Of course, Hiro becoming pregnant was a medical impossibility, so he wasn't too concerned about that. All the same, it felt really dirty- even the bare possibility that they, two siblings could reproduce- only accelerated how objectionable this whole thing was. Hiro should know better, but it just felt too good to resist, and fuck if Tadashi cared.

But none of it mattered.

"I love cumming inside my big brother... " Tadashi clung to Hiro, and buried his face in the man's collar. "I wanna do it every day." Hiro felt smitten by him somehow. Perhaps, as Tadashi got older, the playing field between them would make a bit more sense. More equal. Until then, he had think of Tadashi as only his little brother. That was enough.

"I love you, Hiro."

"I love you too." He kissed Tadashi's cheek and held him close. It was a sleepy, quiet moment, rudely interrupted by something loud and thundering outside. "Wait- did you hear that?"

In their car parked by the vacant building, a couple hours had slipped by. The parade came and went, and the festivities would continue long into the night. Fortunately, they were in no hurry to get home. Tadashi peeled himself away, and they did a cursory enough job of cleaning up and fixing their clothes, enough for the younger Hamada to dart out of the car to see what was going on. Hiro noticed Tadashi's phone had fallen out onto the seat, and that the battery was long dead. The thing before was just an act. He put it back on Tadashi's seat, and heard the fireworks outside.


End file.
